An understanding of basic boat wiring is a necessity for any boat owner or operator. Any discussion with a marine technician will highlight the fact that often times a boat’s operational problems are related to its electrical system.
When you install basic boat wiring, the distance from the power supply to the component and back must be calculated. Once this is done, you can use a formula supplied by organizations such as the American Boat and Yacht Council to determine the thickness (gauge) of wiring that should be used.
Do not solder a connection. Solder connections are susceptible to vibration damage and if heated could fail completely leaving you without power for your electrical component.
Crimp style connections are more appropriate for the marine environment. First crimp the connection and then use adhesive-lined heat-shrink material to seal it from the environment. You will find detailed information on making boat electrical connections on our boat wiring page.
The wet, corrosion-inviting marine environment warrants a higher grade of wiring and connections than land applications. A boat’s electrical system should be fitted with properly sized tinned copper wire and cables with marine rated insulation.
Using undersized wire and cable in even one circuit on a boat is an invitation to disaster. Wire too small for the job can quickly heat up and fail and leave you at risk for an onboard electrical fire. Bottom line: Always use the right size and grade of wire for the job. Our boat wire page goes into detail on how to select the right wire.
Batteries
House and engine batteries should always be separated electrically so if you were to run your house battery down accidentally you wouldn’t have to worry about killing your engine starting battery. Your engine/starting battery should be isolated so you can start the engine(s) at any time. Ideally, you should have at least one battery for each engine and a battery bank for your house power.
Even relatively small boats with single outboard power should be outfitted with a pair of batteries. Battery terminals should always be covered either by a battery box cover or individual terminal covers. A battery switch should be installed on a boat. With any multiple battery installation you should be able to select each battery individually.
Bus Bars
Any top notch boat electrical system will be outfitted with bus bars for specific purposes. For example, even on a small boat like my sons 20-foot Seacraft we installed a two pairs of bus bars. One large pair called the main bus consists of a power and ground bus bar and is designed to handle the majority of gear on the boat. This bus pair is switched off or on using the battery selector switch. Another smaller pair called the battery bus is powered all the time whether the battery switch is on or off. The battery bus is designed to power the bilge pump and high water alarm, both of which need to be powered at all times. A larger vessel would of course have many more bus bars.
Basic Boat Wiring—What to Look for in a New Boat
The care and attention to detail that a boatbuilder gives to the vessel’s electrical system is often illustrative of the entire boat’s quality and workmanship. So if the wiring behind the helm controls consists of a disorganized gaggle of wires, there is a good chance you’re dealing with a subpar boat and builder.
However, if the wiring is neatly bundled and loomed, and there are no uncovered terminals or hanging wires, the rest of the boat will probably stand out in the quality, fit and finish and safety categories. Boats from manufacturers like Contender, Cabo, and Tiara have top-notch marine-wiring installations on all their new boats.
We named a few quality boatbuilders who are known for excellent wiring installations. Another smart practice these builders follow is to label the wiring and connections throughout the boat.
More Basic Boat Wiring Quick Tips
- Boaters should use a protective spray-on coating on connections and terminals.
- If you add electrical equipment make sure wire or cable is sized right.
- Turn off all power by removing the positive battery cable before starting any work.
- All electrical equipment on a boat should have a circuit breaker or fuse.
- Use a breaker or fuse sized according to recommendations by the equipment manufacturer.
- A fundamental of boat wiring: Never tap into another wire for power.
- Start a circuit at a positive bus bar terminal or terminal block and ground bus bar.
- Keep a record of any new wires, cables, or electrical equipment you install.
- Clamp all wiring securing. Use tie wraps to secure wire in bundles for a clean, neat installation.
- Avoid using wing nuts on battery terminals, boat vibration can loosen them, use lock nuts instead.
One last important piece of advice to remember about basic boat wiring is this: It is much different than wiring for a car or a home. In short, the wiring on a boat needs to be bigger, tougher and more durable due to the corrosive effects of saltwater and salt air, the pounding a boat at takes sea, and the sometimes high level of vibration found on boats. Prepare your boat’s wiring for the worst and it will reward you with years of trouble-free service.